Connecting a pipeline or flowline bundle to a subsea production facility can be a very arduous and time consuming procedure, particularly in deep water. Depending upon the connection technique employed, if the pipeline is laid outside a specific target area, literally months can be spent correcting the error. This is not hard to understand once it is appreciated that the pipeline may be hundreds or even thousands of feet below the pipelay vessel, relatively immobile, and difficult to remotely manipulate. One method for approaching this problem is the so-called lateral deflection technique covered by U.S. Pat. No. 4,145,909. In accordance with that technique, a pipeline is deliberately laid to one side of and somewhat past the subsea production facility, and subsequently the pipeline is bent or deflected to make connection with the facility. This technique, while operable, nonetheless suffers from several drawbacks. First, the pipe ends must be laid down into a rather small target area and a means of pulling the pipe end toward the subsea production facility must be established. Second, the lateral deflection technique is at the mercy of unpredictable soil behavior as the pipeline must be pulled across often treacherous terrain as it sweeps toward the subsea production facility. Thus, the approach angle of the pipeline to the production facility is often unpredictable because of boulders or other obstacles which disrupt the motion of the pipeline as it is deflected toward the production facility. This latter problem may be overcome to some extent by cleaning the area over which the pipeline is to be deflected or by supporting the pipe off-bottom with a system of buoys and chains as described in U.S. Pat. No. 4,145,909. The lateral deflection technique has the further disadvantage that the area swept out by the pipe as it is deflected toward the subsea facility is large and this area is then unavailable for the installation of other equipment. A related drawback resides in the stresses introduced into the pipeline not only because of boulders and other obstacles in the path of deflection which, in an extreme case, may buckle the pipeline but also in the backward and lateral pulling on the pipeline necessary to deflect it toward the production facility. Even further, the lateral deflection technique is unduly complicated, requiring one or more tow vessels, as well as a drilling vessel to (1) land a pull-in tool onto a large sled at the end of the pipeline, (2) establish a connection between the sled and a pullcable carried by the pull-in tool, (3) pay out the pullcable between the sled and the production facility, (4) land the pull-in tool on the production facility, and finally (5) perform the deflection and pull-in operations.
Applicant is not aware of any other prior art which, in his judgment as one skilled in the pipeline art, would anticipate or render obvious this novel pipelay technique of the present invention; however, for the purposes of fully developing the background of the invention and establishing the state of the requisite art, the following art is set forth: U.S. Pat. No. 3,431,739.